It is almost certain that two female crew of a yacht berthed at a jetty near Bowness in Lake Windermere in Britain were killed by carbon monoxide poisoning. The skipper and partner of one of the crew also suffered breathing difficulties but he survived. The third crew member was a ten-year-old girl, the daughter of the dead woman.

Lake Windermere - the tragedy unfolds - .. .

The victims have been named as Kelly Webster, 36, and Lauren Thornton, 10, of Leyland, Lancashire. The survivor was Matthew Eteson, 39, also of Leyland. Eteson raised the alarm after he suffered breathing difficulties, and the two were airlifted from Windermere to Royal Lancaster Infirmary where they died.

Carbon monoxide poisoning is known as the 'silent killer' because it is undetectable to humans. (See Sail-World story).

It is understood the theory of the deaths of the two women involves the use of a generator on the boat, which may have been faulty and put carbon monoxide into the boat instead of piping it outside.

A spokeswoman said: 'Police were alerted by the ambulance service after it was reported three people on a privately-owned boat were having serious breathing difficulties.

'On arrival, Mrs Webster and her daughter, Lauren, were being treated by paramedics and were airlifted to Royal Lancaster Infirmary, where they tragically died.

'Police are not treating the deaths as suspicious, and it is suspected that the deaths were caused by some form of gas poisoning. Inquiries continue to be conducted by officers on behalf of the coroner.'

Lake Windermere - mother and daughter died, skipper survived - .. .

What is carbon monoxide poisoning?Carbon monoxide is released when a fuel burns with insufficient oxygen - incomplete combustion. Inhaling it reduces blood's ability to carry oxygen, leaving organs and cells starved of oxygen Humans cannot smell or see the poisonous gas - which is why it is dubbed a silent killer

How can you tell the symptoms?The symptoms of mild carbon monoxide poisoning may be non-specific and similar to those of viral cold and flu infections or food poisoning: headache, nausea, abdominal pain, dizziness, sore throat and dry cough.